Electrochemical and corrosion behaviour of reinforced steel embedded in cement pastes incorporating different amounts of silica fume as a partial replacement of cement has been studied in chloride and sulphate solutio...Electrochemical and corrosion behaviour of reinforced steel embedded in cement pastes incorporating different amounts of silica fume as a partial replacement of cement has been studied in chloride and sulphate solutions by using different electrochemical techniques. The results indicate that, while steel passivity degree is low in the control samples' upon soaking in the corrosive media, it has been high in samples incorporating silica fume and increased with increasing silica fume content. The improvement effect of silica fume may be attributed to the pore solution structure of the cement paste, which limits the mobility of aggressive ions near the surface of the steel. The mechanism of steel corrosion due to chloride and sulphate attack and passivation effect of silica fume are discussed.展开更多
Conductivity of glasses in the systems SiO2.PbO.RO, (where R=Ca, Sr or Ba) was investigated between room temperature and 530 K. The dependence of log resistivity as well as the activation energy on the PbO content has...Conductivity of glasses in the systems SiO2.PbO.RO, (where R=Ca, Sr or Ba) was investigated between room temperature and 530 K. The dependence of log resistivity as well as the activation energy on the PbO content has been studied. Based on the present experimental results, the possible different conduction mechanisms in such glasses are discussed. It was postulated that Pb2+ ions may represent the major charge carrying species in these glasses. This assumption was confirmed by the calculations of the mean distance between the interstitial Pb2+ ions and the effective center of the O2- ions in the glass networks. The variation in the values of the density and the molar volume with PbO content is also discussed in view of the obtained activation energies for the studied glass-systems.展开更多
文摘Electrochemical and corrosion behaviour of reinforced steel embedded in cement pastes incorporating different amounts of silica fume as a partial replacement of cement has been studied in chloride and sulphate solutions by using different electrochemical techniques. The results indicate that, while steel passivity degree is low in the control samples' upon soaking in the corrosive media, it has been high in samples incorporating silica fume and increased with increasing silica fume content. The improvement effect of silica fume may be attributed to the pore solution structure of the cement paste, which limits the mobility of aggressive ions near the surface of the steel. The mechanism of steel corrosion due to chloride and sulphate attack and passivation effect of silica fume are discussed.
文摘Conductivity of glasses in the systems SiO2.PbO.RO, (where R=Ca, Sr or Ba) was investigated between room temperature and 530 K. The dependence of log resistivity as well as the activation energy on the PbO content has been studied. Based on the present experimental results, the possible different conduction mechanisms in such glasses are discussed. It was postulated that Pb2+ ions may represent the major charge carrying species in these glasses. This assumption was confirmed by the calculations of the mean distance between the interstitial Pb2+ ions and the effective center of the O2- ions in the glass networks. The variation in the values of the density and the molar volume with PbO content is also discussed in view of the obtained activation energies for the studied glass-systems.
